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\(ab\left(x-y\right)^3-8ab=ab\left[\left(x-y\right)^3-2^3\right]=ab\left(x-y-2\right)\left[\left(x-y\right)^2+2\left(x-y\right)+4\right]\)
\(36x^2-y^2+6y-9=36x^2-\left(y-3\right)^2=\left(6x-y+3\right)\left(6x+y-3\right)\)
\(8x^2+10x-3=0\)
\(8x^2-2x+12x-3=0\)
\(2x\left(4x-1\right)+3\left(4x-1\right)=0\)
\(\left(4x-1\right)\left(2x+3\right)=0\)
\(\left[\begin{array}{nghiempt}4x-1=0\\2x+3=0\end{array}\right.\)
\(\left[\begin{array}{nghiempt}4x=1\\2x=-3\end{array}\right.\)
\(\left[\begin{array}{nghiempt}x=\frac{1}{4}\\x=-\frac{3}{2}\end{array}\right.\)
\(\left(2x-5\right)^2-\left(x+4\right)^2=0\)
\(\left(2x-5+x+4\right)\left(2x-5-x-4\right)=0\)
\(\left(3x-1\right)\left(x-9\right)=0\)
\(\left[\begin{array}{nghiempt}3x-1=0\\x-9=0\end{array}\right.\)
\(\left[\begin{array}{nghiempt}x=\frac{1}{3}\\x=9\end{array}\right.\)
B1 :
a, B = (x+1)^2+(y-2)^2 = (99+1)^2+(102-2)^2 = 100^2+100^2 = 20000
b, = (2x^2+16x+32)-2y^2
= 2.(x+4)^2-2y^2
= 2.[(x+4)^2-y^2] = 2.(x+4-y).(x+4+y)
c, <=> (x^2-3x)+(2x-6) = 0
<=> (x-3).(x+2) = 0
<=> x-3=0 hoặc x+2=0
<=> x=3 hoặc x=-2
B2 :
P = (3-x).(x+3)/x.(x-3) = -(x+3)/x = -x-3/x
k mk nha
Bai 1
a)B=(x+1)2+(y-2)2
Voi x=99,y=102
=>B= 1002+1002
=20000
b)\(2x^2-2y^2+16x+32\)
=\(2\left[\left(x^2+8x+16\right)-y^2\right]\)
=\(2\left[\left(x+4\right)^2-y^2\right]\)
=2(x-y+4)(x+y+4)
c)\(x^2-3x+2x-6=0\)
=>x(x-3)+2(x-3)=0
=>(x-3)(x+2)=0
=>x=-2;3
Bai 2
\(P=\frac{9-x^2}{x^2-3x}\)
=\(-\frac{x^2-9}{x\left(x-3\right)}\)
=\(-\frac{\left(x-3\right)\left(x+3\right)}{x\left(x-3\right)}\)
=\(\frac{-x-3}{x}\)
a)a+b+c=9
=>(a+b+c)2=81
=>a2+b2+c2+2ab+2bc+2ca=81
Từ a2+b2+c2=141=>2ab+2bc+2ca=81-141=-60
=>2(ab+bc+ca)=-60=>ab+bc+ca=-30
b)x+y=1
=>(x+y)3=1
=>x3+3x2y+3xy2+y3=1
=>x3+y3+3xy(x+y)=1
=>x3+y3+3xy=1(Do x+y=1)
c)a3-3ab+2c=(x+y)3-3(x+y)(x2+y2)+2(x3+y3)
=x3+3x2y+3xy2+y3-3x3-3y3-3x2y-3xy2+2x3+2y3=0
d)đang tìm hướng giải
a) y3 + 12y2 + 48y + 64
= (y + 4)(y2 - 4y + 16) + 12y(y + 4)
= (y + 4)(y2 - 4y + 16 + 12y)
= (y + 4)(y2 + 8y + 16)
= (y + 4)(y + 4)2
= (y + 4)3
b) y3 - 6y2 + 12y - 8
= (y - 2)(y2 + 2y + 4) - 6y(y - 2)
= (y - 2)(y2 + 2y + 4 - 6y)
= (y - 2)(y2 - 4y + 4)
= (y - 2)(y - 2)2
= (y - 2)3
a; y^3 + 12y^2 + 48y + 46
= y^3 + 3 . 4 . y^2 + 3 . 16 . y + 64 - 18
= ( y + 8 )^3 - 18
= ( 6 + 8)^3 - 18
= 14^3 - 18
Cái 46 phải là 64 thì phải
b, = ( y - 2)^3 = ( 22 - 2 )^3 = 20^3 = 8000
a) \(A=x^2-4y^2+x-2y\)
\(=\left(x-2y\right)\left(x+2y\right)+\left(x-2y\right)\)
\(=\left(x-2y\right)\left(x+2y+1\right)\)
Thay vào
b) tương tự
Tại x=1 ; y=2 thay vào BT ta có
A= \(1-4.2^2+1-2.2=\)-18
ý b) cũng thay v thoy
x2-2xy-9z2+y2
= ( x2-2xy+y2 ) -9z2
=(x-y)2-(3z)2
=(x-y-3z)(x-y+z)
Thay x=6;y=-4;z=30 ta có:
(6+4-90)(6+4+90)
=(-80).100
=-8000
Hk tốt